. >> reporter: three years after dennis brooks had his arthritic hip replaced, he began to feel the pain. it became so bad that he just had his hip replacement replaced. >> i was depressed that i had to go through this again because as far as i was concerned, they didn't do their research. >> reporter: brooks' original hip replacement was made entirely of metal and that appears to have been the problem. something his new surgeon, dr. steven harwin, says he sees all too often. >> i've never been an advocate for metal on metal hips. i was skeptical about some of the results when we had these early reports of failure. >> reporter: hip replacements are a great medical success story, versions made of ceramic and plastic, but some new artificial hips are entirely metal. and for the estimated half a million americans who now have metal on metal hips, the news hasn't been good. johnson & johnson recalled their all-metal hip in 2010. a deposition revealed a 2011 internal company document predicted that almost 40% of those hips would go bad within five years. johnson & johnson says that estimate w